In every filtering process the problem exists that as the products removed from a stream by a filter build up a layer on the filter medium the efficiency of the filter is reduced more and more. This problem has proven to be particularly significant in the field of carbon black production. In this technology the stream of smoke or carbon black-containing gas is passed through filters and carbon black forms a relatively compact cake on the filter. Currently this carbon black cake is removed by shutting off the flow of the smoke and backflushing the filter, for instance with filter off-gas from another filtering unit which is on filtering cycle. However, this backflushing technology is not as sufficiently effective as desired.
Other technology has been developed in order to sufficiently remove the material filtered from a stream and accumulated on the filter surface. Thus, for instance, in the field of carbon black collection, the filter bags were subjected to a mechanical treatment such as beating in order to remove carbon black cake from the surface. This treatment created problems, particularly as far as the time of use of the filters was concerned, because the mechanical treatment was quite damaging to the filter medium and oftentimes reduced the period of use of the filter medium.